1. Technical Field of the Invention
This invention relates generally to portable electronic equipment and more particularly to an integrated circuit of a multi-function handheld device that employs a memory having an overlay space to import instructions from external memory.
2. Description of Related Art
As is known, integrated circuits are used in a wide variety of electronic equipment, including portable, or handheld, devices. Such handheld devices include personal digital assistants (PDA), CD players, MP3 players, DVD players, AM/FM radio, a pager, cellular telephones, computer memory extension (commonly referred to as a thumb drive), etc. Each of these handheld devices include one or more integrated circuits to provide the functionality of the device. For example, a thumb drive may include an integrated circuit for interfacing with a computer (e.g., personal computer, laptop, server, workstation, etc.) via one of the ports of the computer (e.g., Universal Serial Bus, parallel port, etc.) and at least one other memory integrated circuit (e.g., flash memory). As such, when the thumb drive is coupled to a computer, data can be read from and written to the memory of the thumb drive. Accordingly, a user may store personalized information (e.g., presentations, Internet access account information, etc.) on his/her thumb drive and use any computer to access the information.
As another example, an MP3 player may include multiple integrated circuits to support the storage and playback of digitally formatted audio (i.e., formatted in accordance with the MP3 specification). As is known, one integrated circuit may be used for interfacing with a computer, another integrated circuit for generating a power supply voltage, another for processing the storage and/or playback of the digitally formatted audio data, and still another for rendering the playback of the digitally formatted audio data audible.
Integrated circuits have enabled the creation of a plethora of handheld devices, however, to be “wired” in today's electronic world, a person may need to posses multiple handheld devices. For example, one may own a cellular telephone for cellular telephone service, a PDA for scheduling, address book, etc., one or more thumb drives for extended memory functionality, an MP3 player for storage and/or playback of digitally recorded music, a radio, etc. Thus, even though a single handheld device may be relatively small, carrying multiple handheld devices on one's person can become quite burdensome.
In some of the handheld devices, an integrated circuit containing a memory, particularly, a random access memory, may be limited in the amount of available memory space. Where such memory space is limited in capacity, it may be difficult to store all of the programs that may be required to operate the handheld device. In order to perform a variety of tasks by executing a number of programs, or at least to have the ability to execute to such programs, some scheme may need to be implemented for the programs if memory capacity is limited. One technique is to swap out programs in the main memory so that a variety of different programs stored in external memory may be executed when needed by the integrated circuit. Accordingly, the embodiments of the present invention address the swapping out of a program from the RAM of the integrated circuit, in order to allow other programs to be executed by the integrated circuit.